In a PCB disposal facility, the reference level for determination of waste oil (treated oil and cleaning solution) after PCB treatment is 0.5 mg/kg. A concentration at the same level as or lower than this reference level indicates no contamination. A verification method therefor is disclosed in “Public Notice of the Ministry of Health and Welfare, No. 192 (appendix 2) of 1992” (Method 1, see Public Notice of the Ministry of Health and Welfare, No. 192 (appendix 2) of 1992), which comprises performing complicated pretreatment for removal of oil components that disturb analysis followed by analysis using a high resolution mass spectrometry.
Meanwhile, it has been revealed that insulating oil in heavy electric equipment such as a transformer (cylindrical transformer) contains trace amount(s) of PCBs. Hence, based on the Act on Special Measures concerning the Promotion of the Proper Treatment of PCB Waste, safe treatment of PCB-contaminated products, such as several million transformers stored in Japan, is required. A PCB concentration level in insulating oil that is the same as or lower than the reference level (0.5 mg/kg) requires no treatment. Accordingly, analysis for determining PCB concentration is important. However, the above verification method is conducted by manually performing complicated pretreatment involving a combination of solvent extraction, solid phase extraction, and sulfuric acid treatment, resulting in significant human error due to differences in degrees of proficiency. Moreover, it is difficult to secure measurement accuracy, and the method takes much time and effort, so that the analysis of several million specimens by such method has been unrealistic.
Meanwhile, various methods for more conveniently analyzing PCBs in insulating oil have been proposed. Examples of such methods include the “Method for Testing Polychlorobiphenyl (PCB) in Service Water•Drainage Water (JIS K0093-2002)” (Method 2, see Method for Testing Polychlorobiphenyl (PCB) in Service Water•Drainage Water (JIS K0093-2002)” (Revised Mar. 20, 2002)), “Japan Electric Association, Regulations concerning Methods for Analyzing Polychlorobiphenyl (PCB) in Insulating Oil (JEAC 1201-1991)” (Method 3; see Regulations concerning Methods for Analyzing Polychlorobiphenyl (PCB) in Insulating Oil (JEAC 1201-1991), Japan Electric Association” (Issued Sep. 30, 1991)), and “Institute of Petroleum Method” (Method 4; see Lecture Proceedings of 44th•45th Japan Society for Environmental Chemistry, 65-74, (Issued Dec. 26, 2007)). All of these methods comprise analyzing PCBs by gas chromatography with electron capture detector. Method 2 comprises performing alkaline degradation and then cleaning up a sample by column chromatography using a normal phase packing material such as silica gel or florisil. Method 3 comprises performing cleanup by sulfuric acid treatment via silica gel column chromatography and silica gel•florisil bi-layer column chromatography, wherein the lower limit of determination is about 2 mg/kg. Method 4 uses sulfuric acid treatment in combination since a correct result cannot be obtained by acetonitrile distribution and silica gel column chromatography alone.
In measurement of low-concentration PCBs in insulating oil, determination of the reference level of 0.5 mg/kg in waste oil is extremely difficult since the nature of PCBs closely resembles the nature of oil components. Examples of an analysis method that addresses such problem include a method (Method 5; see JP Patent Publication (Kokai) No. 2006-313125 A) that is a combination of the bi-layer column chromatography of Method 3 and sulfuric acid treatment and a method that involves extracting PCBs from insulating oil using a polar solvent (preferably, dimethyl sulfoxide) and then applying the polar solvent used for PCB extraction through a solid-phase extractor, so as to separate a PCB fraction (Method 6; see JP Patent Publication (Kokai) No. 2000-88825 A). Also, examples of a method that involves performing liquid chromatography instead of conventional column chromatography include a method that involves separating PCBs from waste oil by gel permeation chromatography using a polystyrene type absorbent based on a difference in molecular weight (Method 7) and a method that involves performing cleanup treatment and fractionation upon analysis of PCBs in environmental samples such as exhaust gas, ash, and drainage water resulting from waste treatment by liquid chromatography (Method 8; see JP Patent Publication (Kokai) No. 2001-83128 A). These methods are characterized by shortened treatment time, cleanup treatment with a small amount of a solvent, and being capable of continuously treating a plurality of samples. However, these methods are intended for environmental samples, so that no lower limit of determination for PCBs in insulating oil is presented.